The Solar System

Planetary Systems

Are there planetesimals and protoplanets outside our solar system?

Since there are already hundreds of confirmed planets and thousands of planet candidates that are known beyond our solar system and that orbit other stars, it is likely that planetesimals and protoplanets exist beyond our solar system as well. Such objects no doubt populate protoplanetary nebulae around other stars. One well-known example is the disk of gas and dust around the star Beta Pictoris, where at least one planet has been discovered. Observations with infrared telescopes, such as the Infrared Astronomical Satellite (IRAS) and the Spitzer Space Telescope, have further detected large numbers of stars surrounded by cocoons of dense dusty gas, where protoplanetary accretions are most likely taking place.